The present invention pertains generally to aerostats and aerostat deployment apparatus. More particularly, the present invention pertains to a compact deployment apparatus that rapidly inflates and deploys an aerostat. The present invention is particularly, but not exclusively, useful as a deployment apparatus that incrementally inflates an aerostat for rapid deployment in windy and otherwise adverse weather conditions.
Tethered lighter-than-air vehicles provide an ideal platform to elevate various payloads. Typical payloads include sensors, communications antennas and relay equipment, cameras and other devices that can take advantage of an elevated position. Typical applications of such devices include telecommunications, electronic warfare, imagery collection, scientific study, aerial advertising, surveillance and television operations. Many of these applications require an elevated platform to be established quickly, with little notice, and without regard to weather conditions.
Heretofore, a typical aerostat inflation and deployment operation has involved a large ground team that can layout and hold the rather large, deflated aerostat, while a lighter-than-air gas is being introduced to inflate the aerostat. These procedures inevitably resulted in large amounts of loose aerostat cloth during inflation that can be damaged in even mild wind conditions. Specifically, the wind can cause the loose aerostat cloth to flap and/or strain, resulting in damage to the aerostat. Additionally, when loose aerostat cloth is present, the wind can cause the location of the Helium inflation xe2x80x9cbubblexe2x80x9d to shift. This shifting of the Helium bubble can also damage the aerostat cloth. In short, these procedures have generally required a large ground team and have been restricted to optimum weather conditions.
In light of the above, it is an object of the present invention to provide apparatuses and methods suitable for rapidly deploying an aerostat in windy conditions. It is another object of the present invention to provide an aerostat deployment apparatus that allows for the incremental inflation and rapid deployment of an aerostat without the requirement of a large ground crew at the deployment site. It is yet another object of the present invention to provide a compact aerostat deployment apparatus that can be easily transported to the deployment site using a light-duty truck. Yet another object of the present invention is to provide an aerostat deployment apparatus and a method for its use that are easy to use, relatively simple to implement, and comparatively cost effective.
The present invention is directed to an apparatus for inflating and deploying an aerostat. For the present invention, the aerostat is preferably an elongated cloth balloon having a nose section at one end and a tail section at the other. The inflation and deployment apparatus includes a substantially cylindrical container for housing the deflated aerostat. The cylindrical container is formed with an open end and defines a longitudinal axis. A feed hose is provided to inflate the aerostat. Specifically, the feed hose passes into the container and extends along the longitudinal axis of the container to a hose end that projects slightly from the open end of the container. The other end of the feed hose is connected to a gas source that is located outside the container.
To position the deflated aerostat on the apparatus, the deflated aerostat is first folded to juxtapose the nose of the aerostat with the tail of the aerostat. Next, the nose of the aerostat is attached to the end of the feed hose that extends from the container opening. A feed port is provided in the nose section of the aerostat to allow lighter-than-air inflation gas to pass from the feed hose and into the aerostat. With the nose section attached to the feed hose and the tail section positioned immediately above the nose section, the remaining portion of the aerostat is folded and inserted into the container. More specifically, the remaining portion of the aerostat is preferably folded into pleats (i.e. similar to the bellows of an accordion) and inserted into the container.
With the above described cooperation of structure, the first portion of the aerostat to inflate when gas passes through the feed hose will be the tail section. As the tail section inflates outside of the container, additional cloth is drawn from the container due to the expanding tail section. Also, wind loading on the exposed portion of the aerostat also tends to draw additional aerostat cloth from the container. Inflation in this manner can be continued until the aerostat is completely inflated, at which point the entire aerostat will be located outside the container. With the aerostat completely inflated, the aerostat can be removed from the feed hose for tethered flight.
Importantly for the present invention, the apparatus includes a restraint mechanism to control the rate of release of aerostat cloth from the container during inflation. Functionally, the restraint mechanism controls the release rate of aerostat cloth to maintain the pressure in the inflated portion of the aerostat within a predetermined range. By maintaining this pressure within a predetermined range, the inflated portion of the aerostat remains taut, preventing damage to the aerostat due to wind loading. As indicated above, loose aerostat cloth can be damaged from flapping or strain caused by wind loads.
In one embodiment of the present invention, the restraint mechanism includes a bowl-shaped member that is positioned at the open end of the container and is centered on the longitudinal axis. A hole formed in the center of the bowl-shaped member allows the member to be installed over the end of the feed hose (i.e. before the deflated aerostat is attached to the feed hose). Springs are provided to bias the bowl-shaped member relative to the feed hose. More specifically, the member is biased away from the end of the of feed hose and toward the container. With the bowl-shaped member installed, the aerostat is folded (as described above) and the nose section of the aerostat is attached to the end of the feed hose. The remainder of the aerostat is draped around the edge of the bowl-shaped member and the pleated body portion of the aerostat is inserted into the container.
As indicated above, inflation of the exposed portion of the aerostat generates forces that tend to draw additional aerostat cloth from the container. Additionally, wind loads on the exposed portion of the aerostat will generate forces that tend to draw additional aerostat cloth from the container. To exit the container, the aerostat cloth must pass around the edge of the bowl-shaped member. The bowl-shaped member, in turn, is biased towards the container by the springs mentioned above. This bias establishes forces on the aerostat cloth that tend to oppose the drawing forces that are generated by the wind and by inflation of the aerostat. For the present invention, the magnitude of these opposing forces can be controlled to maintain the pressure in the inflated portion of the aerostat within a predetermined range. More specifically, the opposing forces can be controlled by the proper design of the springs.
In another embodiment of the present invention, the restraint mechanism includes a friction sheet. For this embodiment of the present invention, the friction sheet is formed with a substantially circular opening that extends through the friction sheet and is located at the center of the friction sheet. Preferably, the opening of the friction sheet is lined by an elastomeric material, such as rubber. The friction sheet is positioned at the open end of the container with its circular opening substantially centered on the longitudinal axis and on the feed hose that extends through the circular opening. With the friction sheet positioned in this manner and attached to the container, the aerostat is folded (as described above) and the nose section of the aerostat is attached to the end of the feed hose. The remainder of the aerostat is then inserted through the circular opening and into the container.
As described above, forces are established during inflation that act to draw additional aerostat cloth from the container. To exit the container, the aerostat cloth must pass through the circular opening in the friction sheet. More specifically, the aerostat cloth must contact and pass over the rubber lining to exit the container. The frictional forces generated while the aerostat cloth contacts and passes over the rubber lining oppose the drawing forces created by wind loads and inflation of the aerostat. By properly sizing the friction sheet, the magnitude of the opposing forces can be controlled to maintain the pressure in the inflated portion of the aerostat within a predetermined range.
In this embodiment, an optional restraining line can be used in conjunction with the friction sheet to control the rate of release of aerostat cloth from the container during inflation. The restraining line extends into the aerostat and terminates at an end that is attached to the tail section of the aerostat. The other end of the restraining line is wrapped around an auto-control braking pulley that is preferably mounted on the feed hose. An optional pressure sensor mounted inside the tail section of the aerostat cooperates with the braking pulley to feed-out a restraining line when the pressure inside the aerostat rises above a predetermined amount. On the other hand, the pressure sensor cooperates with the braking pulley to prevent restraining line feed-out when the pressure inside the aerostat falls below a predetermined amount. Thus, the rate of aerostat cloth release can be controlled by the restraining line to maintain the pressure in the inflated portion of the aerostat within a predetermined range.
In the preferred embodiment of the present invention, the container is mounted on a two-axis gimbal. The attachment points of the gimbal are positioned on the container to allow the container to independently rotate about the longitudinal axis of the container, and about a transverse axis that is normal to the longitudinal axis. Preferably, the transverse axis passes through the container near the container""s open end. For the present invention, the feed hose and restraint mechanism (i.e. friction sheet or bowl-shaped member) also rotate with the container on the two-axis gimbal. A weathervane is preferably attached to the canister. The two-axis gimbal and weathervane cooperate to orient the tail section of the aerostat downwind during inflation. This insures that the rigging is properly oriented on the bottom of the aerostat. In another embodiment, the two-axis deployment gimbal is oriented manually in a manner to insure that the tail section of the aerostat is deployed downwind with the rigging on the bottom.